In RAID-5, the data and parity are distributed across multiple disks, rather than having dedicated drives for each. Read performance is very high because essentially all but one drive is operating in striped mode. If one disk has failed, the array continues to operate by calculating the information from the missing disk on the fly, a process that slows performance. At all times, writing data to the array is complicated because of the need to re-calculate parity stripes. Whenever data smaller than a full stripe is written, the existing data must be re-read to be incorporated into the parity calculation, resulting in what is known as the read-modify-write cycle. Overall write performance slows significantly compared to a regular striped array. The Promise FastTrak S150 SX4 requires the installation of a memory module on the board. This memory is used to buffer and speed up the parity calculations.

The XOR parity calculations and the RAID-5 distribution algorithms require a significant amount of processing power, even assuming modern processors. Traditional RAID-5 controllers contain an expensive, embedded processor to handle these calculations. The FastTrak S150 SX4, on the other hand, runs the RAID-5 algorithms on the main CPU and runs the profuse but simpler XOR parity calculations using a less expensive chip on the controller. According to the product overview, the "Promise FastTrak S150 SX4 employs a hardware XOR engine to offload the heavy-duty RAID 5 parity calculations while leveraging a small percentage of very fast Pentium host CPU processing power to perform RAID algorithms." This tradeoff results in a controller that provides a high performance RAID-5 solution at a cost under $200.